Circuit-controlling apparatus.



L. G. NICHOLSON. CIRCUIT OONTROLLING APPARATUS.

APPLICATION FILED JULY 22, 1908. v 959,787. Patented May 31, 1910.

3 SHEETS-SHEET l.

M H x y M 1 W m P. N M/w -1 j@ r l I l 1 Il. 11111111111 L. C.NICHOLSON.

CIRCUIT GONTROLLING APPARATUS.

Patented May31, 1910.

3 SHEETS-SHEET 2,

`PPLICVATION PILE'D JULY 22, 1908.

ma www: W.

S141) @w to@ L. o. NICHOLSON.

- CIRCUIT GONTROLLING APPARATUS.

APPLICATION FILED JULY 22, 1908.

Patented May 31, 1910.

. 3 SHEETS-SHEET 3.

A TTORNEYJ' WITNESSES UNITED STATES PATENT OFFICE.

LLOYD CARLTON NICHOLSON, OF BUFFALO, NEW YORK.

CIRCUIT-CONTROLLING APPARATUS.

To all 'whom it may concern:

Be it known that I, LLOYD C. NICHOLSON, a citizen of the United States,and a resident of Buffalo, county of Erie, State of New York, haveinvented certain new and useful Improvements in Circuit-ControllingApparatus, of which the following is a specification.

My invention relates to the protection of transmission lines from theresults of a fault developed on any conductor of the line.

My invention is especially applicable to polyphase transmission lines,although some features of my invention have utility apart from their useon a polyphase transmission line.

It is customary in transmitting power of high tension over considerabledistances to supply two or more independent transmission lines connectedtogether both at the power and at the receiving ends of the line, thusenabling either line to be employed in case the other or others are putout of commission. It is desirable to disconnect both ends of atransmission line upon which the ground occurs and to do so with aslittle injury or strain to the power station as possible.

One ob]l ect of my invention is to provide a system having only twoparallel transmission lines connecting the power and receiving stationsand so arranged as to disconnect a faulty transmission line at both endsof the line immediately upon the development of a fault in the line andregardless of the position of the fault. Certain means for disconnectinga faulty line have been heretofore proposed but they fail in practiceunless more than two transmission lines are provided, or unless there isa generating station at each end of the line.

Another object of my invention is to provide apparatus for automaticallycutting out the faulty line that will act positively and certainlyregardless of any unequal division of the working load between the twotransmission lines and regardless of whether branch load lines areconnected to one or other transmission line between the power andreceiving stations, and regardless of any differences that may exist inthe lengths of the different transmission lines or their conductivecapacities.

More specific objects of my invention will Patented May 31, 1910.

Serial No. 444,711.

l appear hereinafter in the course of the description of the illustratedembodiments of my invention.

vide two parallel polyphase transmission lines connected together at thepower and receiving stations and in each line I place two circuitbreakers, one at or near each of the stations. At or near each station Ialso provide apparatus in each transmission line with circuits extendingtherefrom, which apparatus supplies no current to said circuits when thelines are in normal condition, but means are provided whereby upondevelopment of a ground upon a conductor of either line the flow ofcurrent thereto causes the apparatus in each line to supply current tothe circuit connected to it. I use these currents in combination in sucha way as to cause them act upon the circuit breaker of the faulty lineto open the same without opening the circuit breaker of the other line.

In order that the development of a ground will cause a current flow toground, a grounded neutral is provided at the power station. Theapparatus for supplying the currents for actuating circuit breakersconsists of series transformers whose secondaries are connected inparallel, there being in each line and at each station a seriestransformer in each conductor of the line. The several secondariesconnected in parallel ordinarily provide no current to the circuitexternal to them because it is well known that the algebraic sum of thecurrents of a polyphase transmission line is equal to Zero. `Themhowever, a ground develops on one of the conductors the secondaries ofeach set of transformers supply a current to the circuit external tothem.

For simplification I will hereinafter refer to the current, that is acurrent corresponding to the algebraic sum of the currents in the threeconductors, as a neutral current. By, using these currents cooperativelyupon apparatus in operative relation with both circuit breakers I amenabled to cause the apparatus to select the faultycircu it breaker andopen it without affecting the other. The two currents thus produced maybe made to coperate to effect this object either by opposing thestrength of one current to the strength of the other current, or bycombining said currents and causing their sum to In accordance with myinvention I proreact with a current having a substantially fixed phaserelation to that of the normal phase of the faulty conductor.

The first form of my invention, namely, where the strengths of the twocurrents are opposed, can be embodied in an extremely simple andeffective apparatus and is one which I prefer to use at the power end ofthe line in all cases, although I do not intend to limit myself to theuse of this form of my invention at the power end. lVhen this form isused at the power end, substantially dilferent strengths of current willbe developed in the two sets of series transformers provided the faultis near enough to the power end so that the impedance of the two pathsto the fault is substantially different. If the fault is so located asto cause the impedance of the two paths to the fault to be very nearlyequal, then the circuit breaker at the power end will ordinarilyY not beopened until after the circuit breaker has opened at the receiving end.After this has occurred the entire current to the fault flows throughthe series transformer at the power end of the faulty conductor, thusproducing a heavy neutral current in the circuit of the secondaries ofthe transformers of which this is one, whereas there will be no currentin the circuit of the secondaries of the transformers in the othertransmission line. In practice I achieve this result by providing anormally balanced relay acted upon oppositely by two coils adjacent toarmatures carried on the relay and movable with the relay, which coilsare respectively connected in the external circuits of the seriestransformers of the two lines. I provide connections from this balancedrelay to the tripping circuits of two circuit breakers so that amovement of the relay in one direction will actuate one circuit breakerand a movement of the relay in the other direction will actuate theother circuit breaker. I also provide means whereby the movement of therelay to one of these operative positions blocks the relay from movementto its other operative position until the circuit breaker has again beenclosed. This same relay may also be employed at the receiving end of theline to actuate the two circuit breakers at that end. In this case,however, where only two transmission lines are supplied additional meansmust be supplied to cause the two neutral currents to act dierently uponthe relay since the current flowing from the power station to groundwill cause the two neutral currents at the receiving end to be equal instrength. IVhere this form of relay is employed it is necessary that thedevelopment of the fault shall cause two neutral currents at thereceiving end which are different in strength and this I effect bysupplying a means for producing a iow of current to the ground throughthe receiving station, the electro-motive-force of which current causesan added current to flow through one of the transformers of the receiving station, while opposing the flow of current through the other ofsaid transformers, the two transformers being those in the faultyconductor and the corresponding conductor of the other line.

IVhatever the specific form of relay employed at the receiving end, itis necessary, because the current to ground from the power end producesequal neutral currents from the series transformers at the receivingend, to provide an additional current which shall so cooperate with thecurrent to ground from the power end through the receiving station as tomake the two neutral currents from the series transformers at thereceiving station act differently upon the relay. In the first form ofmy invention, already briefly described, this different action iseffected because the additional current makes the strength of one of theopposing currents of the relay greater than that of the other.

In another form of my broad invention I provide the series transformerswith their secondaries connected as before, the two sets of transformersbeing reversely connected to a single circuit. Across this circuit Iconnect a coil or coils which will receive the sum of the currentssupplied to the external circuit by these transformers. In this case therelative phase of the current developed in this coil or coils when aground occurs depends upon which conductor contains the fault. Vith anygiven phase of the grounded current the current in the coil or coilswill be either substantially of the same phase or of relatively oppositedirection. In this case, therefore, it is only necessary to prov vide asecond current which has a definite phase relation to the groundedcurrent and to provide means whereby this second currentl may coact withthe current in the coil or coils in order to cause the operation of arelay in one direction or another to produce the actuation of the propercircuit breaker. The current in the coil or coils connected to the setsof series transformers has a phase and direction dependent upon thephase that is grounded and the line containing the grounded conductor.The second current supplied to a co-acting coil or coils has a phase anddirection that is definitely related to the phase and direction of thegrounded current and is not different whether one or the other linecontains a grounded conductor, This second current may be supplied invarious ways. Vhether the form of relay at the receiving end be onedependent upon the opposing strength of one of the neutral currents ofthe series transformers to the strength of the neutral currents of theother transformers or whether it be one dependent upon the opposing orcombined current from the cross-connected sets of secondaries of theseries transformers, the second current that is to be supplied from thereceiving end must have a definite phas-e relation with the groundcurrent. With either form of relay this second current may be suppliedby providing as one of the power transformers at the receiving station aset of transformers having star connected primaries with a groundedneutral, and the secondaries connected in delta. In this case, through aretransformation, a current will be generated in the grounded primaryand if the apparatus is properly designed, this current flowing throughthe faulty conductor at the receiving station to the fault and hencethrough the ground to the neutral at the receiving station will cause aneutral current from the series transformers of the faulty line at thereceiving station to be greater' than that in the neutral of the seriestransformers of the' other line. A series transformer may be supplied inthe grounded neutral at. the receiving station, the secondary of whichsupplies the current in the same phase as that of the groundedconductor, which current may be used in various ways to effect theproper operation of the relay, as for example, by supplying coils whichco-act magnetically with those supplied by the series transformers atthe receiving station.

I have illustrated my invention in the accompanying drawings in which-Figure l is a diagram illustrating a power' station and a receivingstation and connected by two tansmission lines and containing apparatusillustrating one embodiment of my invention. Fig. 2 is a diagramillustrating a modified form of my invention at the receiving station.Figs. 3, t, and 5k are respectively side, top and end views of the relayused at bot-h stations in the system of Fig. l.

In the present application I have shown and will describe the specificform of my invention illustrated in Fig. 2 for the purposeofillustrating the scope of my present invention, but I do not make anyclaim to this specific embodiment as this forms in part the subjectmatter of another application filed on an even date herewith.

Referring to Fig. l, A indicates three transformers at the power stationsupplying a three phase current to the three station buses l, 2, 3. Thestar connected secondaries khave a neutral a connected to ground asindicated. 4t, 5, 6 are the buses at the receiving station which may beand ordinarily are in such systems a number of miles distant from thepower station. The power and receiving stations are connected by thetransmission lines 7, 8, 9 and 10, Il, 12, which are tied together ateach end by the buses.

B represents a set of power transformers at the receiving end, havingtheir primaries star connected and their secondaries delta connected. Cand C represent circuit breakers in the power station adapted todisconnect the respective lines from the buses in the power' station. Dand D are similar circuit breakers in the receiving station adapted todisconnect the other ends of the transmission lines from the receivingstation buses. E and E indicate batteries constituting sources of powerrespectively from the power and receiving stations for supplying currentto tripping and closing circuits of the circuit breakers, these circuitsbeing represented by broken lines. c, c', CZ and (Z represent thetripping coils of the four circuit breakers, the circuit breakers beingactuated to open the circuit when their respective tripping coils areenergized by the closure of the tripping circuit. e, f, g and 7L arecoils for closing the circuit breakers, these coils being in circuitsconnected to the batteries and controlled by the hand switches Ze.

The relay used at both ends in Fig. l is structurally illustrated inFigs. 3 to 5. This relay has a pivoted arm L carrying iron armatures Z,the arm being pivoted in the center and normally balanced between theopposing springs Z. This arm is acted upon oppositely by coils M, M ofelectro-magnets suitably supported upon base N below the armatures Z. Ifsubstantially unequal currents are supplied to these coils M, M, the onehaving the greater current will attract its armature and move. the armin one direction or another from its balanced position. By doing so oneof the tripping circuits is closed between one of the contacts m carriedat the ends of the arm and the spring m suitably supported from the baseN.

O, O', O2 and O3 are coils for operating stops for the arm L, each pair(O and O; O2 and O3) of coils being adapted to act oppositely upon oneof the common cores 0 each of which engages a pivoted stop or blockingmember 0. Each common core with. its stop 0 has two positions. When thesetting coil is energized the stop is thrown to a vertical position toblock arm L, and when its releasing coil is energized it is thrown to aninclined position, permitting said arm to move in either direction, thestop remaining in its last operated position until again positivelymoved. Coils O and O2 are in the respective tripping circuits so thatwhen coil M, for example, has attracted its armature, closing thetripping circuit of the coil c to open circuit breaker C, then coil O2at the opposite end of the relay operates upon its locking arm o to pullthe arm to the vertical position and preventing the movement of therelay in the direction to open circuit breaker C after circuit breaker Chas opened. This would otherwise take place because after circuitbreaker C is opened and before the circuit breaker D opens (provided thefault is in such a location as to cause C to open before D) then all thecurrent to ground will pass through the line containing circuit breakerC. In the same way if the fault has been one in the conductors 10, 11,12 causing magnet M to operate the relay to open circuit breaker C, themovement of the relay energizes coil O and causes it to raise itsblocking arm 0. The blocking arms 0 are moved from under the arm L so asto iur lock the same by the coils O, O3 which are respectively in theclosing circuits of the closing coils f, e, whereby when the fault hasbeen repaired and the circuit breaker has again closed the stop istilted and arm L is free to move in response to the energization ofeither of the coils M or M.

The coils M, M, are connected respectively to the external circuits ofthe parallelly connected secondaries of two sets of series transformers,P, P. The set of transformers P comprises three transformers whoseprimaries are in series in the transmission lines 7, 8 and 9 at thepower station, while the set of transformers P are similar transformersplaced in the conductors 10, 11, 12 at the power station. Beforeconsidering in further detail what occurs at the receiving station andthe necessities at that point, T will point out the operation of theapparatus thus far described at the power station. X indicates a faultin the form of a ground developed in the transmission line 12. Prior tothe development of this fault the relay arm is in the balanced positionshown in Figs. 1 and 3, and no current is flowing in the coils M or Mbecause the only currents passing over the transmission lines are thepower currents, the algebra-ic sums of these currents being equal tozero. Before the development of the fault, also, all the circuitbreakers are closed, while the tripping and closing circuits thereof areopened. Upon the development of the fault at X current will flow to thefault from the bus 3 taking two paths to the fault, one through theconductor 12 and the other through the conductor 9, bus Ll and distantend of conductor 12, the two paths uniting at the faultand flowingthrough the earth to the neutral (L of the star connected powersecondaries. These two currents produce currents in the neutrals of thetwo sets of series transformers atthe power station and thereforecurrent is supplied both to the coil M and to the coil M. 1f the twotransmission lines have equal conductivity, the current in the coil Mwill be the greater, the extent of this being dependent upon theposition of the fault along the conductor 12.

le can assume for purposes of considering the specic operation of thesystem, that the two lines are of equal conductivity, although this isnot at all essential to my invention, it being one object of myinvention to supply an operative and efficient means whatever therelative conductivity of the two lines. Vfhere the lines differ inconductivity the coils M and M, or the two sets of transformers, aredesigned diiferently. 1f the fault X is not too close to the distantreceiving station the current in coil M will be sufficiently greaterthan that in the coil M to cause the lever L to be actuated to close thetripping circuit of the tripping coil c, thus opening the circuitbreaker C. The faulty line is thus disconnected at the power end. Theaction of the blocking and unblocking coils has already been described.If the fault X is so close to the receiving station that the currents inthe two paths to the fault are so nearly equal that relay L is notactuated, then the circuit breaker C will not be opened until after thecircuit breaker D at the other end of the faulty line has been opened aswill be hereinafter explained. 1f circuit breaker D has opened all thecurrent flowing to the fault will flow through the conductor 12 and noneof it through the conductor 9 which will cause a heavy current to flowthrough the coil M and none through coil M, resulting in the opening ofcircuit breaker C.

Referring now to the receiving station, I have shown similar sets ofseries transformers P2, P3, acting upon the coils M and M of the relayat the receiving station. which relay is in the specific embodiment ofFig. 1 identical with that shown at the power station and its parts aredesignated by the same reference letters. It will be noted that anycurrent from the power station passing through tlie conductor 12 at thereceiving station to the fault must necessarily be received through thebus 3, the conductor 9 and the bus i- Therefore, any grounded currentfrom the power station that would tend to produce a current in the coilM of the relay at the receiving station will also cause an equal currentin the coil M at the receiving station. 1t is necessary, therefore, toprovide some additional means in order to actuate the relay in thereceiving station. This I have provided in the case of Fig. 1 byemploying at the receiving station power transformers whose primariesare star connected and whose secondaries are delta connected, the starconnected primaries having a grounded neutral at a. Upon the developmentof the fault at X the primary between the bus et and the groundedneutral no longer acts as a primary since both ends are grounded, butbecomes a secondary which supplies current having anelectro-motive-force that will oppose the flow of the grounded currentfrom the power station through the line 9 and will add to the currentflowing through the conductor 12 at the receiving station M. Thiscurrent produced in the coil of the transformers B that is connected tothe bus 4 is generated because the powerl current supplied to the othertwo primaries produces a secondary current in the three delta connectedsecondaries, and this current in the grounded transformer produces aretransformation in the grounded primary. In the specific instance ofFig. 1, therefore, the relay at the receiving station is made to respondto and actuate the proper circuit breaker because the power transformerat the receiving' station is so arranged and connected as to produce acurrent to ground, the electro-motive-force of which is so applied as toincrease the neutral currents from the transformers P2, while decreasingthe neutral currents in the transformers P2. In every case where onlytwo transmission lines are employed it is necessary in order to obtainthe proper action upon the circuit breakers at the receiving station, toproduce a current in the receiving station that will coact with thecurrents produced by the flow of current from the power station throughthe receiving station to the fault.

In Fig. 2 I have illustrated another method of embodying the broadprinciple of my invention in order to indicate the scope thereof. Inthis figure I have shown only the .receiving station, it beingunderstood that the power station may be exactly as in Fig. 1. Forpurposes of explanation it will again be assumed that the fault is inconductor 12 at some pointV outside of the receiving station. Thetransformers P2, P3, the circuit breakers D and D with their trippingand closing coils and circuits supplied by the battery E are or may beconstructed and arranged as in Fig. 1. The power transformers in thesystem of Fig. 2 are illustrated as having delta. connections both fortheir primaries and their secondaries, it being immaterial whatconnections of transformers are employed. In this case the two sets ofparallel connected secondaries of the series transformers P2, P3, areoppositely connected together so that they have a single externalcircuit which will receive a current that is a resultant of the currentsproduced by each set of secondaries. IVhere there is no fault on theline neither set of secondaries will supply any current to the externalcircuit. If, however, a fault has developed in the conductor 12, thenthe current passing through conductor 9, bus 4; and conductors 12 to thefault will pass through the two transformers and will tend to causeequal currents from the two sets of secondaries, which currents are ofopposite phases. Inasmuch as the two transformers are connectedoppositely to their external circuit, a single resulting currentwill besupplied to that circuit. As the two sets of transformers are connectedoppositely to each other, the current developed in the circuitconnecting them will have a direction depending upon whether the faultyconductors are in one line or the other. I take advantage of this factto connect to the external circuit of these sets of transformers, coilsM2 and M3 in which the currents generated by the two sets oftransformers unite as a resultant current so that any apparatus uponwhich these coils act will be acted upon cooperatively by the twocurrents produced by the two sets of transformers. The exact phase ofthe current in these coils is determined by the fact that the fault isin the line 12. Six possible phases of current can be found in thesecoils, depending upon which line is at fault and in which conductor ofthat line the fault has developed. Opposed to these coils are coils Q, Qwhich are supplied with a current having a definite phase relation tothe normal phase of the grounded conductor, the phase of the current inthese coils being independent of the line in which the fault hasdeveloped, thus the phase of the current in coils M2 and M2, due to thefault in the line 12 is exactly opposite to that which would occur ifthe fault had developed in the line 9, whereas I so supply the coils Qand Q that the phase of the current is exactly the same whether thefault be in the conductor 12 or the conductor 9. I connect one set ofthese coperating coils as M2, l\ 3 in reverse series, while connectingthe other pair of coils as Q, Q in straight series, one set of coils asM2, M3 may be secured to the pivoted relay arm L1, while the other setas Q, Q is fixed in position to coact respectively with the coils h 2,M2. With the relative phases, as above described, it is obvious thatAwhatever the fault developed, one of the coils M2, hf 2 will beattracted by the adjacent coil Q, Q, while the other of said coils willbe repulsed by the adjacent coil. Ihile in this specific embodiment Ihave shown two sets of coils, it is obvious that the two sets only actcumulatively when applied to a single relay arm L, and that either ofthe sets shown, M2 and Q or M3 and Q, operate to produce oppositemovements of the relay arm according to which line is at fault.

I have illustrated in Fig. 2 one way of supplying to the coils Q, Q acurrent that will have a definite phase with relation to the normalphase of the grounded conductor. The means I have shown involve theproduction of a current in the coils Q, Q that is determined by the flowof current to the fault, although this is not an essential to theprovision of such a current.

R is a set of potential transformers having star connected primaries anddelta connected secondaries. The neutral of the star is connected toground by conductor a2, in which conductor is placed a limitingresistance 7" and a series transformer fr. secondary of this transformersupplies the coils Q, Q. Then the arm is in normal condition there is nocurrent in the conductor a2 and therefore no current is supplied to thecoils Q, Q. Upon the development of a faultin any conductor, thusshort-circuiting one of the three primaries of the transformer set It,the current produced in the three secondaries by induction from the twoungrounded primaries causes a re-transformation of energy to cause thegrounded primary to act as a secondary and supply a current through thefaulty conductor, thence through the ground and through the neutral c2.This current causes a current to be supplied by the secondary oftransformer r thereby supplying a current to coils Q, Q whose phase isdefinitely related to that of the grounded conductor. Thus in thepresent instance with a ground assumed on conductor 12, the bus -t isthe ground bus and the primary between that bus and the center of thestar will be the one that supplies cur- `rent to coils Q, Q and thiscurrent will necessarily have a definite phase relation to the normalphase of conductor 1:2. If the fault had developed on conductor 9instead of on conductor 12 it would not affectthe phase of the currentproduced by transformer 7'.

The relay arm L by its movement. in one direction or another controlsone or other of the tripping circuits exactly as in the case of therelay in Fig. 1. Inasmuch as the current iiowing from the power endthrough the receiving station to the fault passes through the twocircuit breakers D and D in series, and also through the sets oftransformers P2 and P3 in series, the opening of either circuitbreakerstops the flow of its current and therefore when the propercircuitbreaker has been actuated by the movement of the arm L there isno longer any grounded current to produce currents in coils M2 and M3,so that there is no danger of the arm moving in the opposite directionand opening both circuit breakers. There is, therefore, no necessity forblocking the relay arm L at the receiving station.

It will be understood that while I have only described two specificembodiments of my invention, other modifications may be made withoutdeparting from my invention, as set forth in the appended claims. I haveshown two embodiments in order to illustrate that in accordance with mybroad invention it is immaterial whether the current produced at thereceiving station (having a definite phase relation to the normal phaseof the grounded conductor) co-acts with the The two currents produced bythe flow of current to ground from the power end, by causing said twocurrents to be of unequal value or by causing them to act selectivelyaccording to their phase.

That I claim as new and desire to secure by Letters Patent is:

1. Two polyphase transmission lines connected at each end, a circuitbreaker in each, a relay arranged to actuate either of said circuitbreakers but normally ineffective, means for producing currentscorresponding respectively to the algebraic sum of the currents in thetwo transmission lines, and means for causing said currents tosimultaneously act upon said relay.

2. Two polyphase transmission lines connected at each end, a circuitbreaker in each, means dependent upon the flow of current to a fault forproducing currents corresponding respectively to the algebraic sums ofthe currents in the two transmission lines, and means for causing saidcurrents to cooperatively act to open the circuit breaker in the faultyline without affecting the other.

3. Two transmission lines connected at each end, a circuit breaker' ineach, conductors normally without current, means for producing twocurrents determined by the tlow of current to a fault in a transmissionline and means supplying said currents to said conductors, and forcausing' said currents to cooperatively act to open the circuit breakerin the faulty line without affecting the other.

4. The combination with a polyphase power station, a receiving station,and two transmission lines connected to the buses at each station, of aseries transformer in each conductor of each line, the transformershaving their secondaries connected in parallel, a coil in the circuit ofeach set of connected secondaries, a relay oppositely acted upon by saidcoils, and a circuit breaker in each transmission line in operativerelation to said relay.

5. Two polyphase transmission lines connected at each end, a circuitbreaker in each, and a relay arranged to operate either breaker and tobe acted upon oppositely by currents each corresponding in value to thealgebraic sum of the currents of the phases of one of the transmissionlines.

6. Two polyphase transmission lines, a circuit breaker in each, trippingcircuits therefor, a relay having positions for closing each trippingcircuit and normally closing neither, and opposing coils acting upon therelay each arranged to receive a current corresponding in value to thealgebraic sum of the currents of the phases of one of the transmissionlines.

7. Two polyphase transmission lines, a circuit breaker in each, trippingcircuits therefor, a relay having positions for closing each trippingcircuit and normally closing neither, opposing coils acting upon therelay each arranged to receive a current corresponding in value to thealgebraic sinn of the currents of the phases of one of the transmissionlines, and means actuated by its movement to either operative positionfor holding it from movement to the other operative position.

8. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for producing currentsdetermined by the flow of current to a fault in any one conductor fromthe power end, means for producing another current having a phasedependent upon which conductor is at fault and definitely related to thenormal phase of a faulty con ductor, and means for causing all of saidcurrents to, co-act to actuate the circuit breaker in the faulty line.

9. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for producing currentsdetermined by the flow of current to a fault in any one conductor fromthe power end, means determined by the flow of current to a fault 4forproducing another current having a phase dependent upon which conductoris at faultv and definitely related to the normal phase of a faultyconductor and means for causing all of said currents to co-act toactu-ate the circuit breaker in the faulty line.

10. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for producing currentsdetermined by the How of current to a fault in any one conductor fromthe power end, means for producing another current having a phasedependent upon which conductor is at fault and definitely related to thenormal phase of a faulty conductor, a relay operatively related to bothcircuit breakers, and means forv causing all of said currents toconjointly act upon said relay.

11. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for producing currentsdetermined by the flow of current to a fault in any one conductor fromthe power end, means responsive to the flow of current to a fault forproducing another current having a phase dependent upon which conductoris at fault and definitely related to the normal phase of the faultyconductor, a relay operatively related to both circuit breakers, andmeans for causing all of said currents to conjoint-ly act upon saidrelay.

12. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for generating a current atthe receiving end flowing to a fault, meansfor producing a currentresponsive to said current and another current responsive to thatflowing to the fault from the power end, and means for causing saidproduced currents to coact to produce a force acting selectively uponsaid circuit breakers.

13. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for generating a current atthe receiving end flowing to a fault and having a definite phaserelation to the phase of the faulty conductor, means for producing acurrent responsive to said current and another current responsive tothat flowing to the fault from the power end, and means for causing saidproduced currents to coact to produce a force acting selectively uponsaid circuit breakers.

14. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, means for generating a current atthe receiving end flowing to a fault, means for producing a currentresponsive to said current and another current responsive to thatflowing to the fault from the power end, two coils respectivelyreceiving said produced currents, and apparatus operatively related toboth circuit breakers and acted upon oppositely by said coils.

15. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, a series transformer in eachconductor of each line at the receiving station, the secondaries of eachset being connected in parallel, a permanent ground at the power end ofthe system, star-delta connected transformers at the receiving station,the star having a grounded neutral, and electro-responsive devicesreceiving the currents from said secondaries and in operative relationto both said circuit breakers.

16. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, a series transformer in eachconductor of each line at the receiving station, the secondaries of eachset being connected in parallel, a permanent ground at the power end ofthe system, star-delta connected power transformers at the receivingstation, the star having a grounded neutral, electro-responsive devicesreceiving the currents from said secondaries and in operative relationto both said circuit breakers.

17. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, a series transformer in eachconductor of each line at the receiving station, the secondaries of eachset being connected in parallel, power transformers at the power endhaving star connected secondaries with a grounded neutral, star-deltaconnected transformers at the receiving station, the star having a,grounded neutral, and

electro-responsive devices receiving the currents from said secondariesand i noperative relation to both said circuit breakers.

18. Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, al series transformer in eachconductor of each line at the receiving station, the secondaries of eachset being connected in parallel, a permanent ground at the power end ofthe system, star-delta connected transformers at the receiving station,the star having a grounded neutral, coils connected respectively to thesaid two sets of secondaries, and a relay oppositely acted upon by saidcoils and in operative relation with both circuit breakers.

lf). Two polyphase transmission lines connected in parallel, a circuitbreaker in each at the receiving end, a series transformer in eachconductor of each line at the receiv ing station, the secondaries ofeach set being connected in parallel, power transformers at the powerend having star connected secondaries with a grounded neutral,star-delta connected transformers at the receiving station, the starhaving a grounded neutral, coils connected respectively to said two setsof secondaries, and a relay oppositely acted upon by said coils and inoperative relation with both circuit breakers.

20. A polyphase power station, a receiving station, a transmissionsystem between the stations made up of two parallel lines connectedtogether at both stations, circuit breakers in each line at thereceiving station, means for producing unequal currents flowing to afault through the conductors of the two lines at the receiving station,and coils receiving currents determined by said unequal currents, saidcoils being in opposite operative relation to said circuit breakers.

2l. A polyphase power station, a receiving station, a t-ransmissionsystem between the stations made up of two parallel lines connectedtogether at both stations, circuit breakers in each line at thereceiving station, means for producing unequal currents flowing to afault through the conductors of the two lines at the receiving station,coils receiving currents determined by said unequal currents, and arelay oppositely acted upon by said coils and operatively related toboth circuit breakers.

22. A polyphase power station, a receiv ing station, a transmissionsystem between the stations made up of two parallel lines connectedtogether at both stations, circuit breakers in each line at thereceiving station, means for producing unequal currents flowing to afault through the conductors of the two lines at the receiving station,series transformers at the receiving station in each conductor of eachline, the secondaries of each set of transformers being connected inparallel, and coils in operative relation to said circuit breakers eachconnected to the circuit of one of the sets of secondaries.

23. A polyphase power station, a receiving station, a transmissionsystem between the stations made up of two parallel lines connectedtogether at both stations, circuit breakers in each line at thereceiving station, means for producing unequal currents flowing to afault through the conductors of the two lines at the receiving station,series transformers at the receiving station in each conductor of eachline, the each set of transformers being connected in parallel, andcoils in opposite operative relation to both circuit breakers eachconnected to the circuit of one of the sets of secondaries.

24;. A polyphase power station, a receiving station, a transmissionsystem between the stations made up of two parallel lines connectedtogether at both stations, circuit breakers in each line at thereceiving station, means for producing unequal currents flowing to afault through the conductors of the two lines at the receiving station,series transformers at the receiving station in each conductor of eachline, the secondaries of each set of transformers being connected inparallel, a relay controlling both circuit breakers, and coilsoppositely acting upon said relay and connected each to the circuit ofone of the two sets of secondaries.

25. A polyphase power station and two parallel transmission linestherefrom, a circuit breaker in each line at the power station, a seriestansformer in each conductor of each line at the power station, each setof transformer secondaries being connected in parallel, a coil connectedto each set of secondaries, and a relay oppositely acted upon by saidcoils controlling both circuit breakers.

26. Two polyphase transmission lines connected in parallel, seriestransformers connected in each conductor of each line, each set oftransformer secondaries being connected in parallel, a coil in thecircuitof each set of secondaries, a pivoted arm oppositely acted uponby said coils, a circuit breaker' in each transmission line, andtripping circuits therefor closed respectively by opposite movements ofsaid arm.

27. Two polyphase transmission lines connected in parallel, seriestransformers connected in each conductor of each line, each set oftransformer secondaries being connected in parallel, a coil in thecircuit of each set of secondaries, a pivoted arm oppositely acted uponby said coils, a circuit breaker in each transmission line, trippingcircuits therefor closed respectively by opposite movements of said arm,means holding said arm from movement to either one of its operativepositions when moved to the other of said positions, and a coil foracsecondaries of tuating said means energized by the movement of the armto close the tripping circuit.

28. Two polyphase transmission lines connected in parallel, seriestransformers connected in each line, each set of transformer secondariesbeing connected in parallel, a coil in the circuit of each set ofsecondaries, a pivoted arm oppositely acted upon by said coils, acircuit breaker in each transmission line, tripping circuits thereforclosed respectively by opposite movements of said arm, means holdingsaid arm from movement to either one of its operative positions afterbeing moved to the other of said positions, a coil for actuating saidmeans energized by the movement of the arm to close the trippingcircuit, a closing circuit for each circuit breaker, and meanscontrolled by the completion of said closing circuit for releasing saidmeans.

29. A power station, two polyphase transmission lines supplied therebyand connected together lat each end, circuit breakers in each line ateach end thereof, a relay at each end of the system controlling bothcircuit breakers thereat, two coils for each relay acting oppositelythereon, and means for supplying to the respective coils currentscorresponding to the algebraic sums of the currents in the respectivetransmission lines at the ends of the lines at which the respectivecoils are located.

30. A power station, two polyphase transmission lines supplied therebyand connected together at each end, circuit breakers in each line ateach end thereof, a relay at each end of the system controlling bothcircuit breakers thereat, two coils for each relay acting oppositelythereon, means for supplying to the respective coils currentscorresponding to the algebraic sums of the currents in the respectivetransmission lines at the ends of the lines at which the respectivecoils are located, and means responsive to the flow of current to afault for producing an inequality of the algebraic sums of the currentsin the transmission lines at the end distant from the power station.

31. A power station, two polyphase transmission lines supplied therebyand connected together at each end, circuit breakers in eachl line ateach end thereof, a relay at each end of the system controlling bothcircuit breakers thereat, two coils for each relay acting oppositelythereon, `a series transformer in each conductor of each line and ateach end thereof, each of the four sets of transformer secondaries beingconnected in parallel, and circuits operatively relating the severalrelay coils to the several sets of connected secondaries,

32. A power station, two polyphase transmission lines supplied therebyand connected together at each end, circuit breakers in each line ateach end thereof, a relay at each end of the system controlling bothcircuit breakers thereat, two coils for each relay acting oppositelythereon, a series transformer in each conductor of each line and at eachend thereof, the four sets of transformer secondaries being connected inparallel, circuits operatively relating the several relay coils to theseveral sets of connected secondaries, and means responsive to the flowof current to a fault for producing an inequality of the currents in thecircuits of the two sets of secondaries at the end distant from thepower station.

33. A power station, two polyphase transmission lines supplied therebyand connected together at each end, circuit breakers in each line ateach end thereof, a relay at each end of the system controlling bothcircuit breakers thereat, two coils for each relay acting oppositelythereon, a series transformer in each conductor of each line and at eachend thereof, each of the four sets of transformer secondaries beingconnected in parallel, circuits operatively relating the several relaycoils to the several sets of connected secondaries, yand star-deltaconnected transformers at the end distant from the power station, thestar primaries having a grounded neutral.

34E. Two parallel polyphase transmission lines, a power station and areceiving station connected thereby, a circuit breaker in each line atthe receiving station, means for producing currents corresponding invalue respectively to the algebraic sums of the currents of the twolines at the receiving station, means for producing a current ofdefinite phase at the receiving station, and means for causing saidcurrents to operatively act to cause the opening of the circuit-breakerof the faulty line.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses.

LLOYD CARLTON NICHOLSON.

Vitnesses:

FRANCES B. H. PAINE, R. O. DowNING.

